Variation Of Tissue Volume Fraction In The Smooth Muscle Layer Along The Length Of Airways

We exposed 21-day-old rats to either normoxia or hyperoxia (greater than 95% O2) for 8 days and assessed in vivo airway responsiveness to aerosolized and intravenous methacholine (MCh) and airway architecture. Airway responsiveness was determined using a plethysmographic method. Hyperoxia increased airway cholinergic responsiveness, as reflected in a decreased mean ED200 (concentration of MCh required to increase respiratory system resistance by 100%) for both aerosolized MCh [air exposed, 5.94 +/- 2.50 vs. O2 exposed, 0.29 +/- 3.34 (SD) mg/ml, P = 0.0013, unpaired t test] and intravenous MCh (air, 1.40 x 10(-8) vs. O2, 2.45 x 10(-10) mol/kg, P = 0.0002). Airway morphometry was studied in a separate cohort of animals. After fixation by distension with Formalin at 25 cmH2O pressure, each airway cross section was photographed, and airway circumference, epithelial area, and smooth muscle layer area were determined by means of contour tracing using a digitizing pad and microcomputer. For the small airways (circumference less than 1,000 microns), hyperoxia increased both mean epithelial thickness (air, 4.88 +/- 0.53; O2, 8.64 +/- 0.90 microns) and mean smooth muscle layer thickness (air, 2.69 +/- 0.11; O2, 4.79 +/- 0.56 microns; P less than 0.0001 for each). O2 had similar effects on the larger (1,000-3,000 microns) central airways (P less than 0.0001 for both layers). We conclude that chronic hyperoxic exposure induces both airway hyperresponsiveness and airway wall thickening in immature rats.

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Origin of Motion in the Human Ureter: Mechanics, Energetics and Kinetics of the Myosin Molecular Motors

Urologia Journal ◽

10.5301/ru.2012.9110 ◽

2012 ◽

Vol 79 (2) ◽

pp. 123-129 ◽

Cited By ~ 1

Author(s):

Romina Vargiu ◽

Anna Perinu ◽

Antonello De Lisa ◽

Frank Tintrup ◽

Francesco Manca ◽

...

Keyword(s):

Smooth Muscle ◽

Molecular Motors ◽

Circular Muscle ◽

Muscle Layer ◽

Shortening Velocity ◽

Smooth Muscle Layer ◽

Circular Smooth Muscle ◽

Longitudinal Smooth Muscle ◽

Human Ureter

Background Ureteral peristalsis is the result of coordinated mechanical motor performance of longitudinal and circular smooth muscle layer of the ureter wall. The main aim of this study was to characterize in smooth muscle of proximal segments of human ureter, the mechanical properties at level of muscle tissue and at level of myosin molecular motors. Methods Ureteral samples were collected from 15 patients, who underwent nephrectomy for renal cancer. Smooth muscle strips longitudinally and circularly oriented from proximal segments of human ureter were used for the in vitro experiments. Mechanical indices including the maximum unloaded shortening velocity (Vmax), and the maximum isometric tension (P0) normalized per cross-sectional area, were determined in vitro determined in electrically evoked contractions of longitudinal and circular smooth muscle strips. Myosin cross-bridge (CB) number per mm2 (Ψ) the elementary force per single CB (Ψ) and kinetic parameters were calculated in muscle strips, using Huxley's equations adapted to nonsarcomeric muscles. Results Longitudinal smooth muscle strips exhibited a significantly (p<0.05) faster Vmax (63%) and a higher P0 (40%), if compared to circular strips. Moreover, longitudinal muscle strips showed a significantly higher unitary force (Ψ) per CB. However, no significant differences were observed in CB number, the attachment (f1) and the detachment (g2) rate constants between longitudinal and circular muscle strips. Conclusions The main result obtained in the present work documents that the mechanical, energetic and unitary forces per CB of longitudinal layer of proximal ureter are better compared to the circular one; these preliminary findings suggested, unlike intestinal smooth muscle, a major role of longitudinal smooth muscle layer in the ureter peristalsis.

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Expression of corticotropin releasing factor (CRF) in the enteric nervous system of the jejunum of sheep

Veterinární Medicína ◽

10.17221/4274-vetmed ◽

2011 ◽

Vol 56 (No. 11) ◽

pp. 551-560 ◽

Cited By ~ 1

Author(s):

A. Czujkowska ◽

MB Arciszewski

Keyword(s):

Nervous System ◽

Smooth Muscle ◽

Muscle Layer ◽

Corticotropin Releasing Factor ◽

Enteric Neurons ◽

Nerve Fibres ◽

Myenteric Neurons ◽

Smooth Muscle Layer ◽

Circular Smooth Muscle ◽

A Minor

 Corticotropin releasing factor (CRF), a 41-amino acid neuropeptide widely distributed in the mammalian central nervous system, has been shown to influence several gastrointestinal functions. Recent studies show that CRF released locally from enteric nerves may also underlie alterations in gut function. In this study, immunohistochemisty was applied to demonstrate the presence of CRF in the jejunum of sheep. Using double immunohistochemical staining the co-localization of CRF with vasoactive intestinal peptide (VIP), galanin, tyrosine hydroxylase (TH), neuropeptide Y (NPY) and substance P (SP) was evaluated. The presence of CRF was detected in myenteric neurons (3.6 ± 0.9%) as well as in submucous neurons (10.5 ± 1.2%). In the ovine jejunum different numbers of CRF-expressing nerve fibres were detected in myenteric ganglia, submucous ganglia, circular smooth muscle layer, lamina muscularis mucosae and between mucosal glands. None of the CRF-positive enteric neurons and CRF-positive nerve fibres exhibited the presence of TH. CRF-immunoreactive (IR) myenteric neurons widely co-expressed VIP and/or NPY. A minor population of CRF-IR myenteric neurons additionally co-stored SP. Galanin was not present in CRF-IR myenteric neurons. The presence of VIP was observed in the vast majority of CRF-positive submucous neurons. Moderate numbers of CRF-IR sumbucous neurons co-expressing galanin or NPY were also found. The presence of SP in CRF-positive submucous neurons was noted only incidentally. In the circular smooth muscle layer CRF-IR/VIP-IR, CRF-IR/NPY-IR as well as CRF-IR/SP-IR nerve fibres were present. In the mucosal layer of the ovine jejunum CRF-IR nerve fibres co-stored additionally VIP, galanin, NPY or SP. This present study provides for the first time evidence that CRF present in different subclasses of enteric neurons may influence certain activities of the ovine jejunum. Co-localization studies indicate that VIP, galanin, SP and NPY functionally co-operate with CRF in the jejunum of the sheep.  

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